Fill in the blanks with the appropriate options: 3. The oxen ... in the field since morning. 4. Your parents are not inferior ... mine in any way. 5. Most people now enjoy ... by air.

Here are the answers to the questions:

3. The oxen .......... in the field since morning.
The subject "oxen" is plural, and the phrase "since morning" indicates an action that started in the past and continues into the present, requiring the present perfect continuous tense. The oxen are performing the action (grazing), so it should be in the active voice.
The correct option is D.
D) have been grazing

4. Your parents are not inferior .......... mine in any way.
The adjective "inferior" is always followed by the preposition "to" when making a comparison.
The correct option is D.
D) to

5. Most people now enjoy .......... by air.
The verb "enjoy" is typically followed by a gerund (the -ing form of a verb).
The correct option is C.
C) travelling